The Caenorhabditis elegans (C. elegans) germ line provides a model for the investigation of molecular controls regulating stem cell maintenance and differentiation into sperm or oocyte. Both GLP-1/Notches signaling as well as FBF/PUF RNA binding proteins contribute to maintain stem cells and promote mitotic cell division. FOG-1/CPEB and FOG-3/Tob proteins regulate the specification of germ cells into sperm. Vertebrate Tob has been suggested to be both a transcriptional regulator as well as an RNA regulator with antiproliferative activity. However, the mechanism by which Tob proteins function is poorly understood. These key regulators are part of a network of genes involved in cellular proliferation, stem cell maintenance and differentiation. Investigating how these regulators work in a simple model system where key questions can be explored will provide insight into how they may work among their conserved vertebrate counterparts. Specific Aims: 1) to develop a chemical method for manipulation of protein stability in C. elegans. 2) To chemically manipulate the presence or absence of key germline stem cell regulators (FOG-3, FBF-1, and LAG-2) and investigate their control of germ cell fate. Study Design: I have applied a new technology to C. elegans for conditionally stabilizing transgenic proteins in vivo. When a Destablization Domain (DD) is fused to a protein of interest, it causes rapid degradation of the fusion protein. However, this fusion protein can be stabilized and rendered functional when treated with a small molecule called Shield1. By placing transgenes under tissue specific regulatory sequences I will be able to control expression of fusion proteins in a spatial and temporal manner. FOG-3, FBF-1, and LAG-2 are conserved regulators of stem cell differentiation and maintenance, respectively, and I plan to use this technology to answer key questions about their function in the germ line that have not been possible with existing approaches. Health Relevance: These studies will contribute to our understanding of the regulation of stem cell maintenance and differentiation. Since the regulation of germ line stem cell maintenance involves genetic regulators which are conserved form C. elegans to mammals, our studies will help to uncover details of how these genes govern stem cell growth and keep them in an undifferentiated state. Investigating the basic components that keep cells in a mitotic growth phase versus causing them to differentiate is essential in our understanding of cancer progression and methods of treatment.